<!doctype html> 
<html> 
<head> 
    <meta charset="utf-8"> 
    <title></title> 
</head>
<body>
<script type="text/javascript">
	
	var b = 10;
	function a(){
		alert(b);
	}
	//a();
	alert(a());//10 undefined


</script>
</body>
</html>